A bearing ring for a roller bearing which constitutes the roller bearing used in vehicles, industrial machines, or the like includes a raceway portion that is in relative rolling contact with a rolling element (a roller). The raceway portion is a portion that receives a load from the rolling element due to the rolling contact with the rolling element, and mechanical characteristics thereof have a great influence on a rolling fatigue life of the roller bearing.
Therefore, a method for improving the mechanical characteristics of the raceway portion and improving the rolling fatigue life of the roller bearing is examined.
For example, as a method for making hardness of the raceway portion (a raceway surface) higher and improving the rolling fatigue life of the roller bearing, using bearing steel on which a carbonitriding process is performed as a steel material of the roller bearing bearing ring is known.
For example, Patent Document 1 proposes a bearing ring of a bearing, in which, by performing high frequency quenching on the surface alone after tempering high carbon chromium bearing steel such as SUJ2 (JIS (Japanese Industrial Standards) G4805), hardness of the surface is set to 700 HV or more, and internal hardness is set to low hardness of 340 to 490 HV, and a method for improving a rolling life of the bearing by using this bearing ring of the bearing.